許多工區進行深開挖工程時，為避免拘限含水層水壓過高，需要針對含水層進行降水，而先前袪水工法之研究文獻主要以Modflow有限差分法(FDM)進行數值模擬，其對水理參數反算與袪水工序模擬與現地擬合良好，但缺乏高階土壤組成率，故無法模擬開挖所造成的地盤反應。本研究團隊利用PLAXIS 3D有限元素法分析(FEM)對深開挖工程進行許多案例及參數研究，研究結果顯示，除了能夠合理預測地盤反應及壁體變位，還能透過此數值分析進行反算分析，得到更適用於各工區之土壤參數。因此為了於深開挖工程中同時考量袪水行為之影響，本研究將探討分析軟體中袪水工法之趨勢性。以目前正在進行的「台北市北投區石牌市場改建案」為主要分析案例，簡化其土壤參數及使用現地水井配置進行研究。研究主軸主要會分成兩部分，第一個部分為驗證並探討袪水工法在數值分析之結果趨勢是否貼近於現地、水理參數反算結果可靠性，並利用反算分析擬合抽水試驗之水井抽水量及水壓變化量，其結果顯示無論是在水壓變化抑或是水井抽水量之推估相當擬合。第二部分則以第一部分為依據，並使用袪水之假設案例探討超額孔隙水壓變化趨勢，以確認分析方法之合理性及結果趨勢性。再以一開挖及袪水之假設案例進行完整開挖之分析，以模擬實際開挖及袪水造成之壁體變位、地表沉陷及開挖區內之隆起趨勢。針對最終研究結果，提出合理且適用於工程界之簡化分析方式。

Many construction sites require dewatering in aquifers to avoid excessive water pressure during deep excavation projects. Earlier research on dewatering methods mainly used Modflow, which is finite difference method (FDM) for numerical simulations and has a certain degree of accuracy in back-analysis hydraulic parameters and simulation of dewatering processes. However, due to the lack of advanced soil constitutive models, it is not possible to simulate the ground reaction caused by excavation. The research team used PLAXIS 3D, the finite element method (FEM), to conducted the analysis of numerous case and parameter studies on deep excavation projects. The researches results showed that, in addition to accurately predicting ground reaction and wall deformation, PLAXIS 3D can also be used for back-analysis to obtain soil parameters that are more suitable for various construction sites. Therefore, to consider the effect of dewatering on deep excavation projects, this study will verify the rationality of dewatering methods by using PLAXIS 3D.This study takes the ongoing "Shihpai Market Redevelopment Project in Beitou District, Taipei City" as the main analysis case, simplifies the soil parameters, and uses the configuration of on-site water wells for research. The main research will be divided into two parts. The first part is to verify and explore whether the results of the dewatering method in the PLAXIS 3D are correct and whether the back-analysis of hydraulic parameters is reasonable. By using back-analysis, the pumping rate and water pressure change of the pumping test can be fitted.The second part is based on the first part to use a hypothetical dewatering case to explore and observe the trend of excess pore water pressure changes to confirm the rationality of the analysis method. Then, a hypothetical excavation case is used with the dewatering method to analyze ground reaction and simulate wall deformation, surface subsidence, and uplift trends within the excavation area. Based on the final research results, a simplified analysis method that is reasonable and applicable to the engineering field is proposed.

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